Rendering is the most visible part of the use of 3D software for architecture. Blender can give the architect a very wide set of tools for expressing his ideas. The user is not limited to preset of render settings, he is free to have the type of render choosen. The integrated post-production tools allow to have realy any visual impact. The integrated engine can produces high quality images when you are used to it. And to make some render quickly and efficiently and if realism is not the aim, the internal engine is a good choice like in the exemples below: When you need more realism, and especialy for interior renderings, you can use othe render engines, like Luxrender or  Yafaray or start to use Cycles, the new rendering engine integrated to Blender like for the following image:

With the node editor, you can get the type of render you want without the use of an other software. The two following images are 100% Blender, for a project that needed a hand drawing touch.